Positive electrode current collector and positive electrode plate, battery, battery module, battery pack, and apparatus containing such positive electrode current collector

ABSTRACT

A positive electrode current collector and a positive electrode plate, a battery, a battery module, a battery pack, and an apparatus including the positive electrode current collector are provided. In some embodiments, a positive electrode current collector is provided, including an organic support layer and an aluminum-based conductive layer disposed on at least one surface of the organic support layer, where the aluminum-based conductive layer contains Al and at least one modifying element selected from O, N, F, B, S, and P, an XPS spectrogram of the aluminum-based conductive layer with a surface passivation layer removed through etching has at least a first peak falling in a range of 70 eV to 73.5 eV and a second peak falling in a range of 73.5 eV to 78 eV, and a ratio x of peak intensity of the second peak to that of the first peak satisfies 0&lt;x≤3.0.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.18/056,248, filed Nov. 16, 2022, which is a continuation ofInternational Application PCT/CN2020/112691, filed Aug. 31, 2020 andentitled “POSITIVE ELECTRODE CURRENT COLLECTOR AND POSITIVE ELECTRODEPLATE, BATTERY, BATTERY MODULE, BATTERY PACK, AND APPARATUS CONTAININGSUCH POSITIVE ELECTRODE CURRENT COLLECTOR”, which are incorporatedherein by reference in their entireties.

TECHNICAL FIELD

This disclosure relates to the field of energy storage, andspecifically, to a current collector and disclosures of the currentcollector in an electrode plate, a battery, a battery module, a batterypack, and an apparatus.

BACKGROUND

Lithium-ion batteries are widely applied to electromobiles and consumerelectronic products due to their advantages such as high energy density,high output power, long cycle life, and little environmental pollution.However, lithium precipitation is likely to occur when the lithium-ionbatteries work under high power, which can easily lead to internal shortcircuit. In addition, the internal short circuit is also likely to occurin abnormal situations where the lithium-ion batteries are squeezed,collided, or penetrated. Therefore, a safety problem with thelithium-ion batteries has limited disclosure and popularization of thelithium-ion batteries to a great extent.

Results of a large number of tests show that the internal short circuitof the batteries are a root cause of safety hazards of the lithium-ionbatteries. To avoid occurrence of internal short circuit of thebatteries, researchers have tried to improve structures of separators,mechanical structures of the batteries, and the like. However, variousdesigns in the prior art are still unable to effectively improve thelithium precipitation occurring when the batteries work under highpower, avoid the occurrence of the internal short circuit of thelithium-ion batteries, or ensure that the batteries can still work afteroccurrence of an abnormal situation in which the lithium-ion batteriesare squeezed, collided, or penetrated.

Therefore, a new battery design solution is required to resolve theabove problem.

SUMMARY

In view of technical problems existing in the prior art, an objective ofthis disclosure is to provide a current collector and an electrode platecapable of improving safety of a battery.

A further objective of this disclosure is to provide a battery capableof preventing thermal runaway and maintaining battery safety underabnormal stresses such as collision, squeeze, penetration, and drop.

To achieve the foregoing invention objectives, a first aspect of thisdisclosure provides a positive electrode current collector, including anorganic support layer and an aluminum-based conductive layer disposed onat least one surface of the organic support layer, where thealuminum-based conductive layer contains aluminum (Al) and at least onemodifying element selected from oxygen (O), nitrogen (N), fluorine (F),boron (B), sulfur (S), and phosphorus (P), an X-ray photoelectronspectroscopy (XPS) spectrogram of the aluminum-based conductive layerwith a surface passivation layer removed through etching has at least afirst peak falling in a range of 70 eV to 73.5 eV and a second peakfalling in a range of 73.5 eV to 78 eV, and a ratio x of peak intensityof the second peak to that of the first peak satisfies 0<x≤3.0.

Based on the current collector in this disclosure, due to the foregoingcharacteristics of the aluminum-based conductive layer, when the currentcollector with a composite structure is subjected to abnormal stressessuch as collision, squeeze, and penetration, the aluminum-basedconductive layer of a relatively thin thickness is prone to rapidcracking or even pulverization at a stress site, and as a result, alocal abnormal stress point of the current collector with the compositestructure quickly loses electrical conductivity. Therefore, when thecurrent collector is used in the battery, a possibility of thermalrunaway caused by short circuit occurring when a battery cell issubjected to abnormal mechanical damage such as penetration, squeeze,and drop can be greatly reduced, which improves a response speed tothermal runaway and significantly reduces short-circuit temperature riseof the battery cell after mechanical damage, thereby greatly improvingthe safety performance of the battery.

In any one of the foregoing embodiments of this disclosure, the ratio xof the peak intensity of the second peak to that of the first peaksatisfies 0.1≤x≤1.5.

In any one of the foregoing embodiments of this disclosure, a peakposition of the first peak is in a range of 72.9 eV±0.6 eV, 72.9 eV±0.5eV, 72.9 eV±0.4 eV, 72.9 eV±0.3 eV, 72.9 eV±0.2 eV, or 72.9 eV±0.1 eV.

In any one of the foregoing embodiments of this disclosure, a peakposition of the second peak is in a range of 74.4 eV±0.6 eV, 74.4 eV±0.5eV, 74.4 eV±0.4 eV, 74.4 eV±0.3 eV, 74.4 eV±0.2 eV, or 74.4 eV±0.1 eV.

In any one of the foregoing embodiments of this disclosure, a thicknessof the aluminum-based conductive layer is D1, and D1 satisfies 0.1μm≤D1≤5 μm, and

In some embodiments, 0.5 μm≤D1≤2 μm. A conductive layer of suchthickness has moderate resistance, is easy to process, and helps improvethe energy density of the battery.

In any one of the foregoing embodiments of this disclosure, an etchingdepth h of the aluminum-based conductive layer and the thickness D1 ofthe aluminum-based conductive layer satisfy 0.1×D1≤h≤0.5×D1, and In someembodiments, 0.3×D1≤h≤0.5×D1. Such etching depth helps obtain anaccurate XPS spectrogram of the conductive layer.

In any one of the foregoing embodiments of this disclosure, themodifying element in the aluminum-based conductive layer is selectedfrom oxygen (O), nitrogen (N), and fluorine (F), and In someembodiments, is oxygen (O). These modifying elements help improve thebrittleness of the conductive layer. When the battery is penetrated byan external foreign object, “point break” can be quickly formed at alocal contact region between the current collector and the foreignobject, and therefore, a possibility of thermal runaway caused by shortcircuit occurring when the battery cell is subjected to abnormalmechanical damage such as penetration, squeeze, and drop can be greatlyreduced, which improves a response speed to thermal runaway, therebygreatly improving the safety performance of the battery.

In any one of the foregoing embodiments of this disclosure, an organicsupport layer material is selected from at least one of polyurethane,polyamide, polyterephthalate, polyimide, polyethylene, polypropylene,polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrenecopolymer, polybutylene terephthalate, poly(p-phenyleneterephthalamide), poly(p-phenylene ether), polyoxymethylene, epoxyresin, phenolic resin, polytetrafluoroethylene, polyvinylidene fluoride,silicone rubber, polycarbonate, and polyphenylene sulfide.

In any one of the foregoing embodiments of this disclosure, penetrationdisplacement of the organic support layer material is less than or equalto 5 mm, In some embodiments, the penetration displacement of theorganic support layer material is less than or equal to 4.7 mm, andfurther In some embodiments, the penetration displacement of the organicsupport layer material is less than or equal to 4 mm. In thisdisclosure, when the penetration displacement of the support layermaterial is lower, deformation of the current collector, a correspondingelectrode plate, and the battery under mechanical damage is alsosmaller, a probability of thermal runaway caused by the short circuit ofthe battery is also lower, so that the battery is safer.

In any one of the foregoing embodiments of this disclosure, an X-rayphotoelectron spectroscopy (XPS) spectrogram of a surface of thealuminum-based conductive layer has at least a third peak falling in arange of 70 eV to 73.5 eV and a fourth peak falling in a range of 73.5eV to 78 eV, and a ratio y of peak intensity of the fourth peak to thatof the third peak satisfies 1.5<y≤4.0. In this way, mechanical strengthof the conductive layer can be further improved, and durability andelectrochemical stability of the current collector with the compositestructure can be significantly improved.

A second aspect of this disclosure further relates to a positiveelectrode plate, including the current collector according to a firstaspect of this disclosure and an electrode active material layer formedon a surface of the current collector.

A third aspect of this disclosure further relates to a battery,including a positive electrode plate, a separator, and a negativeelectrode plate, where the positive electrode plate is the positiveelectrode plate according to the second aspect of this disclosure.

A fourth aspect of this disclosure further relates to a battery module,including the battery according to the third aspect of this disclosure.

A fifth aspect of this disclosure further relates to a battery pack,including the battery according to the third aspect of this disclosureor the battery module according to the fourth aspect of this disclosure.

A sixth aspect of this disclosure provides an apparatus, including atleast one of the battery according to the third aspect of thisdisclosure, the battery module according to the fourth aspect of thisdisclosure, or the battery pack according to the fifth aspect of thisdisclosure.

Because the conductive layer of the positive electrode current collectorin this disclosure is prone to rapid cracking or pulverization at thestress site in the abnormal stresses such as collision, squeeze,penetration, and drop, the local abnormal stress point of the currentcollector with the composite structure quickly loses electricalconductivity and “point break” is formed shortly. Therefore, thepossibility of thermal runaway of the battery using the currentcollector can be reduced, which improves the response speed to thermalrunaway. Therefore, the electrode plate, the battery, and the apparatusin this disclosure have improved safety performance.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic structural diagram of a positive electrode currentcollector according to a specific embodiment of this disclosure;

FIG. 2 is a schematic structural diagram of a positive electrode currentcollector according to another specific embodiment of this disclosure;

FIG. 3 is a schematic structural diagram of a positive electrode plateaccording to a specific embodiment of this disclosure;

FIG. 4 is a schematic structural diagram of a positive electrode plateaccording to another specific embodiment of this disclosure;

FIG. 5 is a schematic diagram of a battery according to a specificembodiment of this disclosure;

FIG. 6 is a schematic structural exploded view of the battery shown inFIG. 5 ;

FIG. 7 is a schematic diagram of a nail penetration test used in thisdisclosure;

FIG. 8 is a schematic diagram of an embodiment of an apparatus using thebattery in this disclosure as a power source;

FIG. 9 is an XPS spectrogram of a positive electrode current collectorin Example 1;

FIG. 10 is an XPS spectrogram of a positive electrode current collectorin Comparative Example 1;

FIG. 11 is a diagram of surface microscopic topography of a currentcollector that is mechanically penetrated by a nail, in Example 1 ofthis disclosure;

FIG. 12 is a diagram of surface microscopic topography of conventionalaluminum foil (the current collector in Comparative Example 1) that ismechanically penetrated by a nail; and

FIG. 13 shows temperature change curves after a nail penetration test ofthe batteries in Example 1 and Comparative Example 1.

In the drawings:

-   -   1—positive electrode plate;    -   10—positive electrode current collector;    -   101—positive electrode organic support layer;    -   102—positive electrode conductive layer;    -   11—positive electrode active material layer;    -   2—negative electrode plate;    -   21—negative electrode current collector;    -   22—negative electrode active material layer;    -   3—separator;    -   4—nail;    -   5—battery;    -   51—housing;    -   52—electrode assembly; and    -   53—cover plate.

DESCRIPTION OF EMBODIMENTS

The following further describes this disclosure with reference tospecific embodiments. It should be understood that these embodiments aremerely used to describe this disclosure but not to limit the scope ofthis disclosure.

For brevity, the present disclosure provides some numerical ranges.However, any lower limit may be combined with any upper limit to form arange not expressly recorded; any lower limit may be combined with anyother lower limit to form a range not expressly recorded; and any upperlimit may be combined with any other upper limit to form a range notexpressly recorded. In addition, each individually disclosed point orsingle numerical value, as a lower limit or an upper limit, may becombined with any other point or single numerical value or combined withanother lower limit or upper limit to form an unspecified range.

In the descriptions of this specification, it should be noted that “morethan” or “less than” is inclusive of the present number and that “more”in “one or more” means two or more than two, unless otherwise specified.

Unless otherwise specified, terms used in this disclosure havewell-known meanings generally understood by persons skilled in the art.Unless otherwise specified, numerical values of parameters mentioned inthis disclosure may be measured by using various measurement methodscommonly used in the art (for example, testing may be performed by usinga method provided in the embodiments of this disclosure).

I. Positive Electrode Current Collector

A first aspect of this disclosure provides a positive electrode currentcollector, including an organic support layer and an aluminum-basedconductive layer disposed on at least one surface of the organic supportlayer, where the aluminum-based conductive layer contains aluminum (Al)and at least one modifying element selected from oxygen (O), nitrogen(N), fluorine (F), boron (B), sulfur (S), and phosphorus (P), an X-rayphotoelectron spectroscopy (XPS) spectrogram of the aluminum-basedconductive layer with a surface passivation layer removed throughetching has at least a first peak falling in a range of 70 eV to 73.5 eVand a second peak falling in a range of 73.5 eV to 78 eV, and a ratio xof peak intensity of the second peak to that of the first peak satisfies0<x≤3.0.

In the prior art, some studies are to improve safety performance oflithium-ion batteries in terms of improving a design of a currentcollector. Herein, a multi-layer current collector with two metal layersand a resin layer sandwiched between the two metal layers is used, sothat as the temperature of the battery increases to a melting point ofthe resin layer, the resin layer of the current collector melts todamage the electrode plate and cut off current, thereby improving thesafety performance of the battery.

However, in many cases, only melting the resin layer to damage theelectrode plate is not sufficiently reliable. The inventors have foundthrough careful research that a conductive layer of a composite currentcollector in the prior art can be further improved and that some specialdesigns can be made to crack and damage the conductive layer of thecomposite current collector in an extreme case to further block thecurrent. In this way, in the extreme case, the conductive layer of thecurrent collector is cracked and damaged to block the current, thesupport layer is heated to melt to further cut off the current, and thetwo together can greatly improve safety of the electrode plate and thebattery.

The inventors have found that when a regular aluminum conductive layerof the composite current collector is doped with some specific elementsand is subjected to specific treatment, a new material structure can beformed in the conductive layer in some cases, thereby further improvingthe safety of the electrode plate and the battery. Without being boundby a specific theory, the inventors believe that when an aluminum bodyof the conductive layer is doped with a specific type of modifyingelement and is subjected to a specific treatment, an aluminum alloy oraluminide having a specific ceramic feature can be formed inside theconductive layer. This aluminum alloy or aluminide has the brittlenessof ceramics. In a case that the battery is impacted, squeezed,penetrated, dropped, and the like, the current collector with thecomposite structure is subjected to a large external force, the organicsupport layer inside the composite current collector can be broken,cracked, or pulverized quickly under action of a conductive layer with abrittle surface, so that a contact region between the current collectorand a foreign object loses electrical conductivity and “point break” isquickly formed. Therefore, when the foregoing current collector with thecomposite structure is used in the battery, a possibility of thermalrunaway caused by short circuit occurring when the battery is subjectedto abnormal mechanical damage such as penetration, squeeze, and drop canbe greatly reduced, which improves a response speed in inhibitingthermal runaway of the battery, thereby greatly improving the safetyperformance of the battery.

In some embodiments, the modifying element may be at least one elementselected from oxygen (O), nitrogen (N), fluorine (F), boron (B), sulfur(S), and phosphorus (P), and In some embodiments, is at least oneelement selected from F, O, and N, and further In some embodiments, isO.

It is difficult to directly observe formation of the aluminum alloy oraluminide of a ceramic nature in the aluminum body, and it is difficultto quantify such formation due to various complex factors such as a typeof the modifying element, a doping amount, a processing method, and acondition. The inventors of this disclosure have an unexpected findingthat by applying X-ray photoelectron spectroscopy (XPS) to the body ofthe conductive layer, it can be easily determined whether the aluminumalloy or aluminide of a ceramic nature exists. Specifically, the X-rayphotoelectron spectroscopy (XPS) spectrogram of the conductive layerobtained with a surface passivation layer removed through etching has atleast a first peak falling in a range of 70 eV to 73.5 eV and a secondpeak falling in a range of 73.5 eV to 78 eV, and the ratio x of peakintensity of the second peak to that of the first peak satisfies0<x≤3.0. When x=0, the conductive layer is a pure aluminum layer, hasgood extensibility, and still has a specific conductive characteristicin the event of mechanical damage. Therefore, when the conductive layeris used to improve safety performance of the battery in the event of themechanical damage, an improvement effect is not stable, especially in alarge-capacity battery cell. However, when x>3.0, electricalconductivity of the aluminum-based conductive layer is greatly reduced,which affects a capability of the aluminum-based conductive layer forcollecting the current and leads to a battery using the aluminum-basedconductive layer to have a large internal resistance, a low dischargecapacity, and a sharp drop in electrical performance such as cycling andrate performance.

In some embodiments, 0.1≤x≤1.5; and in some other embodiments,1.5<x≤3.0. A minimum value of the ratio x can alternatively be 0.1, 0.2,0.3, 0.4, 0.5, 0.8, 1.0, 1.2, 1.3, 1.4, or 1.5; and a maximum value ofthe ratio x can alternatively be 2.8, 25 2.5, 2.2, 2.0, 1.5, 1.4, 1.3,1.2, 1.1, or 1.0.

To obtain the XPS spectrogram of the body of the conductive layer, thepassivation layer on the surface of the conductive layer needs to beremoved before the XPS spectrogram measurement. This is because metalaluminum is oxidized when exposed to air and forms an oxide passivationlayer on a surface. Direct XPS measurement of the conductive layerwithout surface treatment interferes with a measurement result. Foraccuracy of the measurement, the conductive layer can usually be etchedto remove 10% to 50% of a total thickness of the conductive layer, andIn some embodiments, 30% to 50% of the total thickness of the conductivelayer. That is, in some embodiments, an etching depth h of thealuminum-based conductive layer and the thickness D1 of thealuminum-based conductive layer satisfy 0.1×D1≤h≤0.5×D1, and In someembodiments, 0.3×D1≤h≤0.5×D1.

In this disclosure, the current collector with the composite structurecan be etched by using a conventional etcher. For example, the surfaceof the current collector can be etched by using an Ar ion etcher at 1-10kV (for example, 3 kV) for 5-60 minutes (for example, 15 minutes). Aspecific measurement condition for the XPS spectrogram measurement canbe easily determined by a person skilled in the art, and a conventionaltest condition (for example, at a test temperature of 25° C.) usuallyused for measuring a metal sample can be used. A person skilled in theart understands that, in the XPS spectrogram, “peak intensity” of aspecific peak refers to a height of the peak in the XPS spectrogram.

It is well known to a person skilled in the art that because of adifference in measurement conditions and an operation error, there maybe a specific error in the peak position in the XPS spectrogram.Depending on the specific measurement condition, the peak (the firstpeak) in the range of 70 eV to 73.5 eV may occur in the range of 72.9eV±0.6 eV, 72.9 eV±0.5 eV, 72.9 eV±0.4 eV, 72.9 eV±0.3 eV, 72.9 eV±0.2eV, or 72.9 eV±0.1 eV. Depending on the specific measurement condition,the peak (the second peak) in the range of 73.5 eV to 78 eV may occur inthe range of 74.4 eV±0.6 eV, 74.4 eV±0.5 eV, 74.4 eV±0.4 eV, 74.4 eV±0.3eV, 74.4 eV±0.2 eV, or 74.4 eV±0.1 eV.

After further study, the inventors of this disclosure believe that thefirst peak near 72.9 eV is a peak representing elemental aluminum (Al⁰),and the second peak near 74.4 eV is a peak representing a compound ofaluminum (Al³⁺), which can indicate existence of an aluminide formed ofaluminum and another modifying element. Therefore, the ratio x of thepeak intensity of the second peak to that of the first peak can indicaterelative amounts of the element aluminum of two valencies (however, x isnot simply proportional to the relative amounts of aluminum of the twovalencies, and also depends on other factors). However, this disclosureis not limited to such theoretical interpretation.

FIG. 1 and FIG. 2 are schematic structural diagrams of a positiveelectrode current collector according to some embodiments of thisdisclosure. FIG. 1 is a schematic structural diagram of a positiveelectrode current collector 10 according to an embodiment of thisdisclosure. Referring to FIG. 1 , the composite current collector 10includes a stacked organic support layer 101 and two conductive layers102 respectively located on two surfaces of the organic support layer101. The organic support layer is configured to hold the conductivelayer, and supports and protects the conductive layer. The conductivelayer is configured to hold an electrode active material layer, andprovide electrons for the electrode active material layer, that is, theconductive layer has functions of conduction and current collection.

It can be understood that, the conductive layer 102 may, in someembodiments, be disposed on one surface of the organic support layer101. For example, FIG. 2 is a schematic structural diagram of a positiveelectrode composite current collector 10 according to another embodimentof this disclosure. Referring to FIG. 2 , the composite currentcollector 10 includes a stacked organic support layer 101 and oneconductive layer 102 located on one surface of the organic support layer101.

A person skilled in the art understands that the composite currentcollector 10 in this disclosure may also optionally include anotherstructural layer. For example, a protection layer (which may be, forexample, a metal oxide) may be additionally disposed on the conductivelayer to protect the conductive layer from chemical corrosion ormechanical damage, and to ensure working stability and service life ofthe composite current collector 10.

[Support layer of Current Collector]

In the current collector in this embodiment of this disclosure, thesupport layer has functions of supporting and protecting the conductivelayer. Because the support layer generally uses an organic polymermaterial or a polymer composite material, density of the support layeris usually lower than density of the conductive layer, which cansignificantly increase the weight energy density of the battery comparedwith a conventional metal current collector.

In addition, the metal layer having a smaller thickness is used, whichcan further increase the weight energy density of the battery. Inaddition, because the support layer can well support and protect theconductive layer on a surface of the support layer, common fracture ofan electrode plate in the conventional current collector is not likelyto occur.

In some embodiments, the material of the support layer may be selectedfrom at least one of an insulating polymer material, an insulatingpolymer composite material, a conductive polymer material, and aconductive polymer composite material.

The insulating polymer material is, for example, selected from at leastone of polyurethane, polyamide, polyterephthalate, polyimide,polyethylene, polypropylene, polystyrene, polyvinyl chloride,acrylonitrile-butadiene-styrene copolymer, polybutylene terephthalate,poly(p-phenylene terephthalamide), poly(p-phenylene ether),polyoxymethylene, epoxy resin, phenolic resin, polytetrafluoroethylene,polyvinylidene fluoride, silicone rubber, polycarbonate, andpolyphenylene sulfide.

The insulating polymer composite material is, for example, selected froma composite material formed of an insulating polymer material and aninorganic material, where the inorganic material is preferably at leastone of a ceramic material, a glass material, and a ceramic compositematerial.

The conductive polymer material is, for example, selected from apolysulfur nitride polymer material or a doped conjugated polymermaterial, such as at least one of polypyrrole, polyacetylene,polyaniline, and polythiophene.

The conductive polymer composite material is, for example, selected froma composite material formed of an insulating polymer material and aconductive material, where the conductive material is selected from atleast one of a conductive carbon material, a metal material, and acomposite conductive material, the conductive carbon material isselected from at least one of carbon black, carbon nanotube, graphite,acetylene black, and graphene, the metal material is selected from atleast one of nickel, iron, copper, aluminum or alloy of the foregoingmetal, and the composite conductive material is selected from at leastone of nickel-coated graphite powder and nickel-coated carbon fiber.

A person skilled in the art can select and determine the material of thesupport layer based on factors such as an actual need of an disclosuresituation and a cost. In this disclosure, the material of the supportlayer is preferably an insulating polymer material or an insulatingpolymer composite material.

A thickness of the organic support layer is D2, and D2 optionallysatisfies 1 μm≤D2≤30 μm, further In some embodiments, 1 μm≤D2≤20 μm, orstill further In some embodiments, 1 μm≤D2≤15 μm.

If the support layer is excessively thin, the mechanical strength of thesupport layer is insufficient, and breakage easily occurs during aprocess such as the electrode plate machining process; or if the supportlayer is excessively thick, volumetric energy density of the batteryusing the current collector is reduced. In addition, the specifiedthickness in this disclosure can further ensure that the currentcollector has great resistance, and significantly reduce a batterytemperature increase when short circuit occurs in the battery.

In some embodiments, penetration displacement of the organic supportlayer material is less than or equal to 5 mm, In some embodiments, thepenetration displacement of the organic support layer material is lessthan or equal to 4.7 mm, and further In some embodiments, thepenetration displacement of the organic support layer material is lessthan or equal to 4 mm. When the penetration displacement of the supportlayer material is lower, deformation of the current collector, acorresponding electrode plate, and the battery under mechanical damageis also smaller, a probability of thermal runaway caused by the shortcircuit of the battery is also lower, so that the battery is safer.

[Conductive Layer of Current Collector]

Compared with a conventional metal current collector, in the currentcollector in this embodiment of this disclosure, the conductive layerhas a conduction function and a current collection function, and isconfigured to provide electrons for the electrode active material layer.Compared with a conventional metal current collector, a thickness of theconductive layer is significantly reduced and density of the organicsupport layer is less than density of metal. This helps reduce weight ofa battery cell and the lithium-ion battery and improve energy density ofthe lithium-ion battery when it is ensured that the conductive layer hasgood conduction and current collection performance.

In the current collector in this disclosure, the conductive layer is analuminum-based conductive layer, that is, a body material of theconductive layer is aluminum or an aluminum alloy. The aluminum alloyused herein may be a conductive alloy formed of aluminum and at leastone metal element selected from copper, nickel, iron, titanium, silver,and zirconium.

In the current collector in this disclosure, in addition to aluminum(Al) (and In some embodiments, another metal element), thealuminum-based conductive layer further includes at least one modifyingelement to form an aluminide of a ceramic nature. The modifying elementmay be at least one element selected from oxygen (O), nitrogen (N),fluorine (F), boron (B), sulfur (S), and phosphorus (P), and In someembodiments, the modifying element is at least one element selected fromF, O, and N, and further In some embodiments, is O. The modifyingelement can be integrated into the aluminum-based conductive layerthrough conventional doping or another method.

In the current collector in this disclosure, with respect to a totalmass of the conductive layer, a weight percentage of the elementaluminum in the aluminum-based conductive layer is 90 wt % or more, andIn some embodiments, 95 wt % or more, and further In some embodiments,98 wt % or more.

In the current collector in this disclosure, with respect to a totalmass of the conductive layer, a weight percentage of modifying elementin the aluminum-based conductive layer is 5 wt % or less, and In someembodiments, 3 wt % or less, and further

In some embodiments, 1 wt % or less.

In accordance with this disclosure, a thickness of the aluminum-basedconductive layer is D1, and D1 usually satisfies 0.1 μm≤D1≤5 μm. In animprovement of the current collector in this disclosure, D1 satisfies 1μm≤D1≤3 μm, and In some embodiments, D1 satisfies 0.5 μm≤D1≤2 μm.

The aluminum-based conductive layer mainly has a function of conductingthe current. If the conductive layer is excessively thin, the currentcollector has a weak current conduction capability and large resistance,is prone to fuse when a large current flows through, and is prone tobreak down during a normal machining process of the electrode plate,which reduces a yield rate; or if the conductive layer is excessivelythick, the volumetric energy density of the battery using the currentcollector is reduced.

For the positive electrode current collector in this disclosure, thealuminum-based conductive layer may be formed on the organic supportlayer through at least one of mechanical roll-in, bonding, vapordeposition (vapor deposition), electroless plating (Electrolessplating), and electroplating. The vapor deposition method is preferablyphysical vapor deposition (PVD). The physical vapor deposition method ispreferably at least one of an evaporating method and a sputteringmethod. The evaporating method is preferably at least one of vacuumevaporating (vacuum evaporating), thermal evaporation deposition(Thermal Evaporation Deposition), and electron beam evaporation method(EBEM). The sputtering method is preferably magnetron sputtering(Magnetron sputtering). For example, an organic support layer ofspecific specifications may be selected, and an aluminum-basedconductive layer of a specific thickness is formed on a surface of theorganic support layer through vacuum evaporating, mechanical roll-in, orbonding. An XPS test is conducted for the aluminum-based conductivelayers to confirm compliance with a requirement of this disclosure

In some embodiments, at least one of vapor deposition, electroplating,or electroless plating is used, so that the support layer and theconductive layer are more firmly bonded.

In an example, a typical process condition for forming the conductivelayer through mechanical roll-in described above is as follows: Thealuminum-based foil is placed in a mechanical roller and rollingcompacted to a predetermined thickness by applying pressure of 20 t to40 t, and then placed onto the surface of the organic support layersubjected to surface cleaning treatment; and finally, the aluminum-basedfoil and the organic support layer are placed in the mechanical rollerto be tightly bonded by applying pressure of 30 t to 50 t. A value rangeof x in the aluminum-based conductive layer is controlled by introducingcorresponding gas (for example, O₂, N₂, and F₂) for reaction during aforming process of the aluminum-based foil.

In an example, a typical process condition for forming the conductivelayer through vacuum evaporating is as follows: An organic support layersubjected to the surface cleaning treatment is placed into a vacuumevaporating chamber, high-purity aluminum wires in a metal evaporatingchamber are melted and evaporated at a high temperature of 800° C. to2000° C., a specific flow of gas (for example, O₂, N₂, and F₂) is alsoinjected into a pinhole cavity, evaporated Al goes through a coolingsystem in the vacuum evaporating chamber, and some Al atoms also reactwith the gas to form an aluminum-based compound, and are finallyco-deposited on the surface of the organic support layer to formmultiple aluminum-based conductive layers.

A typical process condition for forming the conductive layer throughbonding is as follows: The aluminum-based foil is placed in a mechanicalroller and rolling compacted to a predetermined thickness by applyingpressure of 20 t to 40 t, and then the surface of the organic supportlayer subjected to surface cleaning treatment is coated with a mixedsolution of PVDF and NMP; and finally, the aluminum-based conductivelayer of the predetermined thickness is adhered to the surface of theorganic support layer and dried at 100° C. A value range of x in thealuminum-based conductive layer is controlled by introducingcorresponding gas (for example, O₂, N₂, and F₂) for reaction during aformation process of the aluminum-based foil.

[Protection Layer of Current Collector]

In accordance with this disclosure, a conductive layer of a currentcollector may further include a first protection layer, the firstprotection layer is located on a surface of the conductive layer(namely, an upper surface of the conductive layer) that faces away froman insulation layer, and the first protection layer contains element Al.

In a further optional embodiment of this disclosure, an X-rayphotoelectron spectroscopy (XPS) spectrogram of a surface of the currentcollector has at least a third peak falling in a range of 70 eV to 73.5eV and a fourth peak falling in a range of 73.5 eV to 78 eV, and a ratioy of peak intensity of the fourth peak to that of the third peaksatisfies 1.5<y≤4.0. The applicants have found through research thatwhen a value of y of the current collector with the composite structureincluding the first protection layer is within the foregoing range, asurface passivation layer of the current collector has strongeroxidation resistance and higher mechanical strength, and the firstprotection layer and the conductive layer are more firmly bonded,thereby further improving durability of the current collector duringdisclosure to a battery system.

It should be noted that the parameters (for example, a thickness andmaterial composition) of the material layers provided in this disclosureall refer to parameters measured for a single-sided material layer. Whenthere are two material layers, parameters of either material layermaking true this disclosure shall be construed as falling within theprotection scope of this disclosure.

II. Positive Electrode Plate

This disclosure further relates to a positive electrode plate, includingthe positive electrode current collector in this disclosure and anelectrode active material layer formed on a surface of the positiveelectrode current collector.

FIG. 3 to FIG. 4 are schematic structural diagrams of positive electrodeplates according to some embodiments of this disclosure. FIG. 3 is aschematic structural diagram of a positive electrode plate according toan embodiment of this disclosure. Referring to FIG. 1 , the positiveelectrode plate includes a positive electrode current collector 10 andtwo positive electrode active material layers 11 respectively formed ontwo surfaces of the positive electrode current collector 10. Thepositive electrode current collector 10 includes a positive electrodeorganic support layer 101 and two aluminum-based conductive layers 102on surfaces of the positive electrode organic support layer.

It can be understood that, when an aluminum-based conductive layer isprovided on one surface of the organic support layer of the positiveelectrode current collector, only one surface of the current collectorcan be coated with an active substance. For example, FIG. 4 is aschematic structural diagram of a positive electrode plate according toanother embodiment of this disclosure. Referring to FIG. 2 , thepositive electrode plate includes a positive electrode current collector10 and a positive electrode active material layer 11 formed on onesurface of the positive electrode current collector 10. The positiveelectrode current collector 10 includes a positive electrode organicsupport layer 101 and one aluminum-based conductive layer 102 on asurface of the positive electrode organic support layer 101. Thepositive electrode plate shown in FIG. 4 can be folded and applied tothe battery.

The positive electrode plate is usually formed with a positive electrodeactive material layer slurry applied and dried. A positive electrodeactive material layer slurry is usually formed by dispersing a positiveelectrode active material and In some embodiments, a conductive agent, abinder, and the like in a solvent and stirring them well. The solventmay be, for example, N-methylpyrrolidone (NMP) or deionized water. Otheroptional adjuvants may be, for example, a thickening and dispersingagent (such as sodium carboxymethyl cellulose CMC-Na) and a PTCthermistor material.

In the battery in accordance with this disclosure, the positiveelectrode active material may be various positive electrode activematerials generally used in the art. Using a positive electrode plate ofa lithium-ion battery as an example, a positive electrode activematerial of the positive electrode plate may include one or more of alithium transition metal oxide, lithium-containing phosphates with anolivine structure, and their respective modified compounds. Examples ofthe lithium transition metal oxide may include but are not limited toone or more of lithium cobalt oxides, lithium nickel oxides, lithiummanganese oxides, lithium nickel cobalt oxides, lithium manganese cobaltoxides, lithium nickel manganese oxides, lithium nickel cobalt manganeseoxides, lithium nickel cobalt aluminum oxides, and modified compoundsthereof. Examples of the lithium-containing phosphates with an olivinestructure may include but are not limited to one or more of lithium ironphosphate, composite materials of lithium iron phosphate and carbon,lithium manganese phosphate, composite materials of lithium manganesephosphate and carbon, lithium manganese iron phosphate, compositematerials of lithium manganese iron phosphate and carbon, and modifiedcompounds thereof. This disclosure imposes no limitation on thesematerials, and other conventional well-known materials that can be usedas the positive electrode active material for the battery can also beused.

In some optional embodiments, to further improve the energy density ofthe battery, the positive electrode active material may include one ormore of the lithium transition metal oxides represented by formula 1 andmodified compounds thereof:

Li_(a)Ni_(b)Co_(c)M_(d)O_(e)A_(f)  formula 1

In the formula 1, 0.8≤a≤1.2, 0.5≤b<1, 0<c<1, 0<d<1, 1≤e≤2, and 0≤f≤1, Mis selected from one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti,and B, and A is selected from one or more of N, F, S, and Cl.

In this disclosure, the modified compounds of the materials may bedoping modification and/or surface coating modification of thematerials.

The electrode active material layer of the positive electrode plate inthis disclosure further optionally includes a binder and/or a conductiveagent.

In an example, the binder used for the electrode active material layermay include one or more of polyvinylidene fluoride (PVDF) andpolytetrafluoroethylene (PTFE).

In an example, the conductive agent used for the electrode activematerial layer may include one or more of superconducting carbon,acetylene black, carbon black, Ketjen black, carbon dots, carbonnanotubes, graphene, and carbon nanofibers.

III. Battery

This disclosure further relates to a battery, including a positiveelectrode plate, a separator, an electrolyte, and a negative electrodeplate, where the positive electrode plate is the positive electrodeplate according to the foregoing second aspect. The battery in thisdisclosure may be of a winding type or a laminated type. The battery inthis disclosure may be one of a lithium-ion battery, a lithium primarybattery, a sodium-ion battery, or a magnesium-ion battery, but is notlimited thereto. During a charging and discharging process of thebattery, active ions are intercalated and deintercalated back and forthbetween the positive electrode plate and the negative electrode plate,and the electrolyte has a function of conducting ions between thepositive electrode plate and the negative electrode plate.

[Negative Electrode Plate]

The battery in this disclosure can use any negative electrode platecommonly used in the art. The negative electrode plate usually includesa negative electrode current collector and a negative electrode activematerial layer.

In the battery in this disclosure, the negative electrode currentcollector can use metal foil or a composite current collector (a metalmaterial can be disposed on a polymer substrate to form a compositecurrent collector). In an example, the negative electrode currentcollector may be copper foil.

In the battery in accordance with this disclosure, the negativeelectrode active material layer usually includes a negative electrodeactive material, an optional binder, an optional conductive agent, andother optional adjuvants, and is usually formed with a negativeelectrode active material layer slurry applied and dried. A negativeelectrode active material layer slurry is usually formed by dispersingthe negative electrode active material, and In some embodiments, aconductive agent, a binder, and the like in a solvent and stirring themwell. The solvent may be, for example, N-methylpyrrolidone (NMP) ordeionized water. The other optional adjuvants may be, for example, athickener and dispersant (such as sodium carboxymethyl celluloseCMC-Na), a PTC thermistor material, and the like.

In an example, the conductive agent may include one or more ofsuperconducting carbon, acetylene black, carbon black, Ketjen black,carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

In an example, the binder may include one or more of styrene-butadienerubber (SBR), water-based acrylic resin (water-based acrylic resin),polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylenevinyl acetate (EVA), polyvinyl alcohol (PVA), and polyvinyl butyral(PVB).

In the battery in this disclosure, the negative electrode activematerial layer may be disposed on one surface of the negative electrodecurrent collector, or may be disposed on both surfaces of the negativeelectrode current collector.

[Electrolyte]

The electrolyte has a function of conducting ions between the positiveelectrode plate and the negative electrode plate. This disclosureimposes no specific limitation on a type of the electrolyte, which canbe selected as required. For example, the electrolyte may be selectedfrom at least one of a solid electrolyte and a liquid electrolyte (orelectrolyte solution).

In some embodiments, the electrolyte is an electrolyte solution. Theelectrolyte solution includes an electrolytic salt and a solvent.

In some embodiments, the electrolytic salt may be selected from one ormore of lithium hexafluorophosphate (LiPF₆), lithiumtetrafluoroborate(LiBF₄), lithium perchlorate (LiClO₄), lithiumhexafluoroarsenate (LiAsF₆), lithium bis(fluorosulfonyl)imide (LiFSI),lithium bistrifluoromethanesulfonimide (LiTFSI), lithiumtrifluoromethanesulfonate (LiTFS), lithium difluoro(oxalato)borate(LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluorophosphate(LiPO₂F₂), lithium difluoro bis(oxalato)phosphate (LiDFOP), and lithiumtetrafluoro oxalato phosphate (LiTFOP).

In some embodiments, the solvent may be selected from one or more ofethylene carbonate (EC), propylene carbonate (PC), ethyl methylcarbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC),dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propylcarbonate (EPC), 1,2-butylene carbonate (BC), fluoroethylene carbonate(FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA),propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP),propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB),1,4-butyrolactone (GBL), tetramethylene sulfone (SF), methyl sulfone(MSM), ethyl methanesulfonate (EMS), and diethyl sulfone (ESE).

In some embodiments, the electrolyte solution may optionally include anadditive. For example, the additive may include a negative electrodefilm forming additive, or may include a positive electrode film formingadditive, or may include an additive capable of improving someperformance of the battery, for example, an additive for improvingover-charge performance of the battery, an additive for improvinghigh-temperature performance of the battery, and an additive forimproving low-temperature performance of the battery.

[Separator]

Batteries with liquid electrolyte and some batteries with solidelectrolyte also include separators. The separator is disposed betweenthe positive electrode plate and the negative electrode plate forisolation. This disclosure imposes no particular limitation on a type ofthe separator, which may be any well-known porous separator with goodchemical stability and mechanical stability. In some embodiments, amaterial of the separator may be selected from one or more of a glassfiber, non-woven, polyethylene, polypropylene polyethylene, andpolyvinylidene fluoride. The separator may be a single-layer thin filmor a multi-layer composite thin film. When the separator is a multilayercomposite film, each layer may be made of the same or differentmaterials.

[Structure and Preparation Method of Battery]

A structure and a preparation method of the battery in this disclosureare well-known.

In some embodiments, a positive electrode plate, a separator, and anegative electrode plate are stacked in sequence, so that the separatoris located between the positive and negative electrode plates forisolation, and then winding (or lamination) process is performed toobtain an electrode assembly. The electrode assembly is placed into anouter package and dried, and the electrolyte is injected. After vacuumpackaging, standing, formation, shaping, and other processes, a batteryis obtained.

In some embodiments, the outer package of the battery may be a hardshell, for example, a hard plastic shell, an aluminum shell, or a steelshell. The outer package of the battery may alternatively be a softpack, for example, a soft pouch. A material of the soft pack may beplastic, for example, one or more of polypropylene (PP), polybutyleneterephthalate (PBT), polybutylene succinate (PBS), and the like.

This disclosure imposes no particular limitation on a shape of thebattery, which may be cylindrical, rectangular, or any other shape.

FIG. 5 shows a rectangular battery 5 as an example. FIG. 6 is aschematic structural exploded view of a structure of the battery 5 inFIG. 5 . Referring to FIG. 6 , the outer package may include a housing51 and a cover plate 53. The housing 51 may include a base plate and aside plate connected onto the base plate, and the base plate and theside plate enclose an accommodating cavity. The housing 51 has anopening connected to the accommodating cavity, and the cover plate 53can cover the opening to seal the accommodating cavity. A positiveelectrode plate, a negative electrode plate, and a separator may bewound or laminated to form an electrode assembly 52. The electrodeassembly 52 is packaged in the accommodating cavity. The electrolyteinfiltrates the electrode assembly 52. There may be one or moreelectrode assemblies 52 in the battery 5, and the quantity may beadjusted as required.

In some embodiments, batteries may be assembled into a battery module,and the battery module may include a plurality of batteries. A specificquantity may be adjusted based on disclosure and a capacity of thebattery module.

In some embodiments, the battery module may be further assembled into abattery pack, and a quantity of battery modules included in the batterypack may be adjusted based on disclosure and a capacity of the batterypack.

During use of the battery, abnormal situations that cause short circuitinclude impact, squeeze, penetration by a foreign object, and the like.Because short circuit is caused in these damage processes by materialswith specific conductivity electrically connecting positive and negativeelectrodes, such abnormal situations are collectively referred to asnail penetration in this disclosure. In addition, in a specificembodiment of this disclosure, abnormal situations of a battery aresimulated through a nail penetration test.

In this disclosure, the nail penetration test is used to simulateabnormal situations of the battery, for observing changes in the batteryafter nail penetration. FIG. 7 is a schematic diagram of one-time nailpenetration test in this disclosure. For brevity, the figure only showsa nail 4 penetrating a one-layer positive electrode plate 1, a one-layerseparator 3, and a one-layer negative electrode plate 2 of the battery.It should be noted that, in the actual nail penetration test, the nail 4penetrates the whole battery, which usually includes a multi-layerpositive electrode plate 1, a multi-layer separator 3, and a multi-layernegative electrode plate 2.

For a conventional lithium-ion battery including a conventional positiveelectrode plate and a conventional negative electrode plate, wheninternal short circuit occurs in an abnormal situation, basically allconventional lithium-ion batteries experience different levels of smoke,fire, explosion, and the like. However, the battery in this disclosurehas a characteristic of confining impact of short-circuit damage on thebattery to a “point” range in a short period of time without affectingnormal use of the battery, which is referred to as “point break”,thereby significantly improving safety of the battery in abnormalsituations. Therefore, this disclosure also relates to the use of thepositive electrode current collector in preparation of a battery thatonly forms point break to protect itself when experiencing an abnormalsituation that causes the short circuit.

In addition, this disclosure also relates to the use of the positiveelectrode current collector as a current collector of a battery thatonly forms point break when experiencing an abnormal situation thatcauses the short circuit.

IV. Apparatus

A fourth aspect of this disclosure provides an apparatus. The apparatusincludes at least one of the battery, the battery module, or the batterypack according to the third aspect of this disclosure. The battery, thebattery module, or the battery pack may be used as a power source forthe apparatus, or an energy storage unit of the apparatus. The apparatusin this disclosure uses the battery provided in this disclosure, andtherefore has at least the same advantages as the battery.

The apparatus may be, but is not limited to, a mobile device (forexample, a mobile phone or a notebook computer), an electric vehicle(for example, a full electric vehicle, a hybrid electric vehicle, aplug-in hybrid electric vehicle, an electric bicycle, an electricscooter, an electric golf vehicle, or an electric truck), an electrictrain, a ship, a satellite, an energy storage system, and the like.

A battery, a battery module, or a battery pack may be selected for theapparatus according to requirements for using the apparatus.

FIG. 8 shows an apparatus used as an example. The apparatus is a fullelectric vehicle, a hybrid electric vehicle, a plug-in hybrid electricvehicle, or the like. To satisfy a requirement of the apparatus for ahigh rate and high energy density of a battery, a battery pack or abattery module may be used.

In another example, the apparatus may be a mobile phone, a tabletcomputer, a notebook computer, or the like. The apparatus usually needsto be light and thin, and the battery may be used as a power source.

The following further describes beneficial effects of this disclosurewith reference to examples.

EXAMPLES

To make the invention objectives, technical solutions, and beneficialtechnical effects of this disclosure clearer, this disclosure is furtherdescribed below in detail with reference to Examples. However, it shouldbe understood that the Examples of this disclosure are merely intendedto explain this disclosure, but not to limit this disclosure, and theExamples of this disclosure are not limited to the Examples given inthis specification. In Examples in which specific test conditions oroperating conditions are not specified, preparation is performedaccording to conventional conditions or according to conditionsrecommended by a material supplier.

I. Preparation of battery Example 1

1. Preparation of organic support layer: The organic support layer couldbe prepared through a conventional casting method, unidirectionalstretching, and bidirectional stretching, or could be commerciallyavailable.

2. Preparation of Current Collector:

The current collector in Example 1 was prepared in a vacuum evaporatingmethod. Specifically, a 6 μm PET substrate film roll was put in a vacuumevaporating chamber, the vacuum evaporating chamber was evacuated to2.5×10⁻³ Pa, a high-purity aluminum wire was fed at a wire feeding speedof 300 mm/min to an evaporation boat heated to 800° C. to 2000° C. formelting and evaporation, high-purity oxygen (with purity of 99.99%) wasalso injected into the vacuum chamber at 300 mL/min, and evaporated Aland alumina obtained through reaction with oxygen were co-deposited on asurface of the organic support layer to form an aluminum-basedconductive layer; and after evaporation was repeatedly performed about20 times, an aluminum-based current collector having a coating of about800 nm in thickness was obtained.

3. XPS Measurement Method for Current Collector:

A PHI quantera XPS tester was used, and a test was performed at roomtemperature of 23±2° C. and relative humidity greater than or equal to65%. Before a test, a surface of the current collector was etched withan Ar ion etcher to remove a passivation layer on the surface, andetching parameters were 3 kV and 15 minutes. An etched current collectorsample was put into the XPS tester for measurement. Data from 8 to 10data points of a same sample was collected for data measurement accuracyand error analysis.

4. Preparation of Electrode Plate and Battery:

(1) Preparation of Positive Electrode Plate

Lithium-nickel-cobalt-manganese ternary active substanceLiNi_(0.8)Co_(0.1)Mn_(0.1)O₂ (NCM811), conductive carbon black Super-P,and polyvinylidene fluoride (PVDF) as a binder at a weight ratio of94:3:3 were fully stirred and evenly mixed in an N-methylpyrrolidonesolvent, to obtain a positive electrode slurry. The positive electrodeslurry was applied onto a positive electrode current collector, andsubjected to processes such as drying, cold pressing, slitting, andcutting, to obtain the positive electrode plate. A compressed density ofthe positive electrode active material layer was 3.4 g/cm³.

(2) Preparation of Negative Electrode Plate

Artificial graphite as a negative electrode active material, SBR as abinder, sodium carboxymethyl cellulose (CMC-Na) as a thickener, andconductive carbon black (Super P) were weighted at a weight ratio of96.2:1.8:1.2:0.8, and the negative electrode active materials anddeionized water were added into a mixing tank in a specific sequence formixing, to prepare the negative electrode slurry. The negative electrodeslurry was applied onto a negative electrode current collector (8 μm Cufoil), and subjected to processes such as drying, cold pressing,slitting, and cutting, to obtain the negative electrode plate. Acompressed density of the negative electrode active material layer was1.6 g/cm³.

(3) Separator

A PE film was selected as the separator.

(4) Preparation of Electrolyte

Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at avolume ratio of 3:7, and then a fully dried lithium salt LiPF₆ wasdissolved in the mixed organic solvent at a proportion of 1 mol/L, toprepare the electrolyte.

(5) Preparation of Battery

A positive electrode plate, a separator, and a negative electrode platewere stacked in sequence and wound to obtain an electrode assembly, theelectrode assembly was put in an outer package, the foregoingelectrolyte was added, and processes such as packaging, standing,formation, and aging were performed to finally obtain the lithium-ionsecondary battery in Example 1.

Example 2

A current collector in Example 2 was prepared in the vacuum evaporatingmethod, with differences from Example 1 in that an oxygen feeding ratewas 800 mL/min, a wire feeding speed was 200 mm/min, and evaporation wasperformed 30 times. Then, a battery electrode plate and a battery wereprepared in a method similar to that in Example 1, but compositions andproduct parameters of the battery electrode plate were varied. Fordetails about different product parameters, refer to Table 1.

Example 3

A current collector in Example 3 was prepared in the vacuum evaporatingmethod, with differences from Example 1 in that gas injected washigh-purity nitrogen (with purity of 99.99%), a gas flow rate was 600mL/min, a wire feeding speed was 240 mm/min, and evaporation wasperformed 25 times. Then, a battery electrode plate and a battery wereprepared in a method similar to that in Example 1. Specific parametersare given in Table 1.

Example 4

A current collector in Example 4 was prepared in the vacuum evaporatingmethod, with differences from Example 1 in that gas injected washigh-purity fluorine (with purity of 99.99%), a gas flow rate was 650mL/min, a wire feeding speed was 270 mm/min, and evaporation wasperformed 22 times. Then, a battery electrode plate and a battery wereprepared in a method similar to that in Example 1. Specific parametersare given in Table 1.

Example 5

A current collector in Example 5 was prepared in the same method asExample 2, and then, a battery electrode plate and a battery wereprepared in a method similar to that in Example 1, but the batterycapacity varied. Specific parameters are given in Table 1.

Examples 6 to 9 and Comparative Examples 1 to 4

Preparation methods of the current collectors, positive electrodeplates, and secondary batteries in Examples 6 to 9 and the currentcollectors and secondary batteries in Comparative Examples 1 to 4 weresimilar to those in Example 3, but materials varied for the organicsupport layer. Specific parameters are given in Table 1 and Table 2.

Example 10

In Example 10, material and thickness of the organic support layer ofthe positive electrode current collector, material and thickness of theconductive layer, and preparation methods of the positive electrodeplate and battery were the same as those in Example 3. A differences wasthat in the preparation process of the positive electrode currentcollector, after the conductive layer was obtained through vapordeposition, first protection layer treatment was added (specifically, asubstrate was put into an oven filled with ozone gas for heat treatment,where an ozone flow rate was 1 L/min, oven temperature was 120° C., andheat treatment duration was 30 minutes).

Example 11

In Example 11, material and thickness of the organic support layer ofthe positive electrode current collector, material and thickness of theconductive layer, and preparation methods of the positive electrodeplate and battery were the same as those in Example 3. A difference wasthat in the preparation process of the positive electrode currentcollector, after the conductive layer was obtained through vapordeposition, first protection layer treatment was added (specifically, asubstrate was put into an oven filled with ozone gas for heat treatment,where an ozone flow rate was 1.5 L/min, oven temperature was 130° C.,and heat treatment duration was 30 minutes).

Example 12

In Example 12, material and thickness of the organic support layer ofthe positive electrode current collector, material and thickness of theconductive layer, and preparation methods of the positive electrodeplate and battery were the same as those in Example 3. A difference wasthat in the preparation process of the positive electrode currentcollector, after the conductive layer was obtained through vapordeposition, first protection layer treatment was added (specifically, asubstrate was put into an oven filled with ozone gas for heat treatment,where an ozone flow rate was 2.0 L/min, oven temperature was 140° C.,and heat treatment duration was 30 minutes).

Example 13

In Example 13, material and thickness of the organic support layer ofthe positive electrode current collector, material and thickness of theconductive layer, and preparation methods of the positive electrodeplate and battery were the same as those in Example 3. A difference wasthat in the preparation process of the positive electrode currentcollector, after the conductive layer was obtained through vapordeposition, first protection layer treatment was added (specifically, asubstrate was put into an oven filled with ozone gas for heat treatment,where an ozone flow rate was 3.0 L/min, oven temperature was 150° C.,and heat treatment duration was 30 minutes).

II. Test methods of battery performance parameters

(1) Rate Test

A lithium-ion battery was charged/discharged at 1 C/1 C at 25° C.Specifically, the lithium-ion battery was first charged to 4.2 V at acurrent of 1 C, and then discharged to 2.8 V at a current of 1 C, and adischarge capacity at 1 C was recorded; and then the battery wascharged/discharged at 2 C/2 C, a discharge capacity at 2 C was recorded,and the discharge capacity at 2 C was divided by the discharge capacityat 1 C, to obtain a capacity retention rate at a rate of 2 C.

(2) Nail Penetration Test:

After being fully charged, the battery was fastened, and a temperaturesensing wire was attached to geometric centers of a nail-penetratedsurface and a back of the battery to be penetrated by a nail, andconnected to a multi-channel thermodetector; a steel nail with a 8 mmdiameter was used to penetrate the battery at a speed of 25 mm/s at roomtemperature, and the steel nail was kept in the battery; and afterpenetration by the nail, the battery was observed, and a five-minutebattery temperature tracking test was conducted, with the batterytemperature at the fifth minute recorded.

III. Test Results of Examples and Comparative Examples

1. Parameters of Positive Electrode Current Collectors and ElectricalPerformance of Batteries:

Table 1 shows specific parameters of the current collectors of thisdisclosure and electrical performance of corresponding battery cells inthe examples and comparative examples.

TABLE 1 Temperature Aluminum-based Capacity rise of cell Organic supportlayer conductive layer First peak Second peak Cell retention after nailThickness Thickness intensity intensity Value capacity rate of cellpenetration Number Material (μm) Material (μm) at 72.9 eV at 74.4 of x(Ah) at 2 C (° C.) Example 1 PET 6 Al/Al₂O₃ 0.8 730 84 0.1 60 93% 6.3Example 2 PET 6 Al/Al₂O₃ 0.8 682 818 1.2 60 90% 2.8 Example 3 PET 6Al/AlN 0.8 869 696 0.8 60 91% 4.8 Example 4 PET 6 Al/AlF₃ 0.8 805 7250.9 60 91% 3.5 Example 5 PET 6 Al/Al₂O₃ 0.8 682 818 1.2 300 89% 5.5Comparative — — Al 12 820 0 0 60 95% 330 Example 1 Comparative PET 6Al/Al₂O₃ 0.8 219 768 3.5 60 75% 2.4 Example 2 Comparative PET 6 Al/Al₂O₃0.8 759 0 0 60 94% 23 Example 3 Comparative PET 6 Al/Al₂O₃ 0.8 759 0 0300 93% 450 Example 4

It can be seen from results in Table 1 that safety performance of thebattery cell (Examples 1 to 4) prepared by using the current collectorin this disclosure was significantly improved compared with that of aconventional Al foil battery cell (Comparative Example 1) with a samecapacity, the battery cell could pass the nail penetration test, thetemperature rise could be controlled within 10° C., and rate performanceof the battery cell was comparable to that of the conventional Al foilbattery cell. In addition, it can be seen that a material of thealuminum-based conductive layer in this disclosure had no obvious impacton electrical performance and the safety performance of the batterycell.

It can be seen from comparison of the Examples with Comparative Examples2 to 4 that a value of a key characteristic x of the aluminum-basedconductive layer required in this disclosure had significant impact onthe electrical performance and safety performance of the battery cell:When x>3.0 (Comparative Example 2), rate performance of a sample batterycell was significantly decreased, and conductivity of the aluminum-basedconductive layer was significantly affected; when x=0, a correspondingsample battery cell (60 Ah, Comparative Example 3) with a small capacitycould also pass the nail penetration test. However, temperature rise ofthe battery cell was already obvious; and when the capacity of thebattery cell became larger, the sample battery cell (300 Ah, ComparativeExample 4) could no longer pass the nail penetration test; or when0<x≤3.0 as required in this disclosure, a corresponding sample batterycell (300 Ah, Example 5) with a large capacity could also pass the nailpenetration test, and the battery cell had no obvious temperature rise.

FIG. 9 and FIG. 10 are XPS spectrograms of a positive electrode currentcollector in Example 1 and Comparative Example 1. In addition, FIG. 13shows time-temperature curves of the batteries in Example 1 andComparative Example 1.

2. Mechanical Nail Penetration Test and Durability Test of CurrentCollector

To better illustrate an action mechanism of the current collector inthis disclosure in improving the nail penetration performance of thebattery cell, the current collector in this disclosure (Example 1) andthe conventional aluminum foil (Comparative Example 1) were mechanicallypenetrated by using a nail and their surface microscopic morphologieswere observed. A steel nail with a diameter of 8 mm was used for themechanical nail penetration, and penetrated through 25 layers of neatlystacked and fastened current collectors at a speed of 25 mm/s, and alocation of a penetration opening at a 10^(th) layer was selected formicroscopic morphology observation under a scanning electron microscope.Morphologies of penetration openings of the current collector in thisdisclosure and the conventional aluminum foil current collector wereshown in FIG. 11 and FIG. 12 separately.

As shown in FIG. 11 and FIG. 12 , after the nail penetration, comparedwith a surface of the conventional aluminum foil, the current collectorin this disclosure showed obvious cracking morphology around thepenetration opening, which indicated that the aluminum-based conductivelayer was obviously damaged after the nail penetration, thereby furtherhindering current conduction around the penetration opening and forminglocal “point break”. This helped avoid the internal short circuitoccurring at the nail penetration opening between the positive andnegative electrodes when the battery cell was damaged after the nailpenetration, and further avoided resulting thermal runaway, therebyimproving the safety performance of the battery cell.

When the penetration displacement of the support layer material waslower, deformation of the current collector, a corresponding electrodeplate, and the battery under mechanical damage was also smaller, aprobability of thermal runaway caused by the short circuit of thebattery was also lower, so that the battery was safer.

Penetration displacement of a support layer material was not onlyrelated to chemical compositions of the material, but also closelyrelated to preparation parameters (heat treatment temperature, duration,a film stretching method, a stretch ratio, and the like) of the materialduring processing.

The penetration displacement test method was as follows:

A Gotech tensile machine was used for the penetration displacement test.A to-be-tested sample was fastened on the Gotech tensile machine with aring clamp, a horizontal plane of the sample was perpendicular to aZ-axis moving shaft of the tensile machine, a ring area was 12.56 cm²(with a diameter of 4 cm), a steel nail with a cross-section area of 1mm² (an end face was hemispherical) penetrated the sample along the Zaxis of the tensile machine at a speed of 50 mm/min, and displacement ofthe steel nail from a time when the steel nail came into contact withthe sample to a time when the sample was penetrated through was measuredand recorded. The displacement was the penetration displacement of thesample.

Current collector durability test method was as follows:

A substrate was punched into 10×10 cm² plate samples, immersed in 100 mLof electrolyte (a LiPF₆ concentration was 1 mol/L, and a volume ratio ofEC/EMC was 7:3) added with 0.1 mm of water, sealed, and put in an ovenat 70° C. for 48 hours of storage. After the storage, the substrate wastaken out, washed with a DMC solvent, and dried. Integrity of a surfacecoating of the substrate was observed and an area of the surface coatingwas measured. Electrolyte durability of the substrate was calculated byusing the following formula: electrolyte durability=coating area afterimmersion and storage (cm²)/initial area of substrate coating (100cm²)×100.

Results of mechanical nail penetration test and durability test ofcurrent collectors are given in Table 2 and Table 3.

TABLE 2 Temperature Organic support layer Aluminum-based Capacity riseof cell Penetration conductive layers Cell retention after nailThickness displacement Thickness Value capacity rate of cell penetrationNumber Material (μm) (mm) Material (μm) of x (Ah) at 2 C (° C.) Example6 PET-1 6 3.8 Al/Al₂O₃ 0.8 μm 0.8 60 Ah 91% 5.3 Example 7 PET-2 6 3.2Al/Al₂O₃ 0.8 μm 0.8 60 Ah 91% 4.8 Example 8 PP 6 4.7 Al/Al₂O₃ 0.8 μm 0.860 Ah 91% 6.7 Example 9 PE 6 6.4 Al/Al₂O₃ 0.8 μm 0.8 60 Ah 91% 36

It can be seen from the foregoing test data that when the penetrationdisplacement of the current collector was less than or equal to 5 mm,temperature rise of the battery cell after the nail penetration wassmaller, and safety of the battery was better.

TABLE 3 Temperature rise of cell Cell after nail Value Third peak Fourthpeak Value capacity Electrolyte penetration Number of x intensityintensity of y (Ah) durability (° C.) Example 10 0.8 527 853 1.6 60 754.2 Example 11 0.8 309 864 2.8 60 88 3.8 Example 12 0.8 261 835 3.2 6094 3.3 Example 13 0.8 221 880 4.0 60 98 2.6 Example 14 0.8 570 809 1.460 53 4.8

In Examples 10 to 13, materials and thicknesses of organic supportlayers of the positive electrode current collectors, materials andthicknesses of conductive layers, and preparation methods of positiveelectrode plates and the batteries were all the same. A difference wasthat in the preparation process of the positive electrode currentcollector, after the conductive layer was obtained through vapordeposition, first protection layer treatment was added. It can be seenfrom Table 3 that when a value of y of a first protection layer on thesurface of the conductive layer was between 1.5 and 4.0, mechanicalstrength of the conductive layer could be further improved, and thefirst protection layer and the conductive layer were also more firmlybonded, so that durability of the current collector with the compositestructure was significantly improved.

Although this disclosure is disclosed above with preferred embodiments,they are not intended to limit the claims. Any person skilled in the artcan make several possible changes and modifications without departingfrom the concept of this disclosure. Therefore, the protection scope ofthis disclosure shall be subject to the scope defined by the claims ofthis disclosure.

What is claimed is:
 1. A positive electrode plate, comprising: a currentcollector comprising an organic support layer and a conductive layerdisposed on at least one surface of the organic support layer; and anelectrode active material layer disposed on the conductive layer,wherein the conductive layer comprises aluminum (Al) and at least onemodifying element selected from the group consisting of oxygen (O),nitrogen (N), fluorine (F), boron (B), sulfur (S), and phosphorus (P),or a combination thereof, wherein an X-ray photoelectron spectroscopy(XPS) spectrogram of the conductive layer has at least a first peakrepresenting elemental aluminum (Al⁰) and a second peak representing acompound containing aluminum (Al³⁺), wherein a ratio x of peak intensityof the second peak to that of the first peak satisfies 0<x≤3.0.
 2. Thepositive electrode plate according to claim 1, wherein the ratio x ofthe peak intensity of the second peak to that of the first peaksatisfies 0.1≤x≤1.5.
 3. The positive electrode plate according to claim1, wherein a peak position of the first peak is in a range of 70 eV to73.5 eV, and a peak position of the second peak is in a range of 73.5 eVto 78 eV.
 4. The positive electrode plate according to claim 1, whereinthe compound containing aluminum (Al³⁺) represented by the second peakis selected from the group consisting of Al₂O₃, AlN, AlF₃, or acombination thereof.
 5. The positive electrode plate according to claim1, wherein a weight percentage of Al in the conductive layer is 90 wt %or more.
 6. The positive electrode plate according to claim 1, wherein aweight percentage of the modifying element in the conductive layer is 5wt % or less.
 7. The positive electrode plate according to claim 1,wherein the organic support layer comprises at least one selected fromthe group consisting of polyurethane, polyamide, polyterephthalate,polyimide, polyethylene, polypropylene, polystyrene, polyvinyl chloride,acrylonitrile-butadiene-styrene copolymer, polybutylene terephthalate,poly(p-phenylene terephthalamide), poly(p-phenylene ether),polyoxymethylene, epoxy resin, phenolic resin, polytetrafluoroethylene,polyvinylidene fluoride, silicone rubber, polycarbonate, polyphenylenesulfide, or a combination thereof.
 8. The positive electrode plateaccording to claim 1, wherein the conductive layer of the currentcollector further comprises a protective layer on a surface of theconductive layer, the protective layer comprising Al.
 9. The positiveelectrode plate according to claim 8, wherein the an X-ray photoelectronspectroscopy (XPS) spectrogram of a surface of the protective layer hasat least a third peak falling in a range of 70 eV to 73.5 eV and afourth peak falling in a range of 73.5 eV to 78 eV, and a ratio y ofpeak intensity of the fourth peak to that of the third peak satisfies1.5<y≤4.0.
 10. The positive electrode plate according to claim 1,wherein the electrode active material comprises one or more lithiumtransition metal oxides selected from the group consisting of lithiumcobalt oxide, lithium nickel oxide, lithium manganese oxide, lithiumnickel cobalt oxide, lithium manganese cobalt oxide, lithium nickelmanganese oxide, lithium nickel cobalt manganese oxide, lithium nickelcobalt aluminum oxide, and a combination thereof.
 11. The positiveelectrode plate according to claim 1, wherein the electrode activematerial comprises one or more lithium-containing phosphates with anolivine structure selected from the group consisting of lithium ironphosphate, lithium manganese phosphate, lithium manganese ironphosphate, and a combination thereof.
 12. The positive electrode plateaccording to claim 1, wherein the electrode active material comprises alithium transition metal oxide represented by formula:Li_(a)Ni_(b)CO_(c)M_(d)O_(e)A_(f), wherein 0.8≤a≤1.2, 0.5≤b<1, 0<c<1,0<d<1, 1≤e≤2, and 0≤f≤1, M is selected from the group consisting of Mn,Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, B, or a combination thereof, and A isselected from the group consisting of N, F, S, Cl, or a combinationthereof
 13. The positive electrode plate according to claim 1, wherein athickness of the conductive layer is D1, and D1 satisfies 0.1 μm≤D1≤5μm.
 14. A battery, comprising: an electrode assembly comprising apositive electrode plate, a separator, and a negative electrode platestacked in sequence, wherein the positive electrode plate comprises: acurrent collector comprising an organic support layer and a conductivelayer disposed on at least one surface of the organic support layer; andan electrode active material layer disposed on the conductive layer,wherein the conductive layer comprises Al and at least one modifyingelement selected from the group consisting of oxygen (O), nitrogen (N),fluorine (F), boron (B), sulfur (S), and phosphorus (P), or acombination thereof, wherein an X-ray photoelectron spectroscopy (XPS)spectrogram of the conductive layer has at least a first peakrepresenting elemental aluminum (Al⁰) and a second peak representing acompound containing aluminum (Al³⁺), wherein a ratio x of peak intensityof the second peak to that of the first peak satisfies 0<x≤3.0.
 15. Thebattery according to claim 14, wherein the ratio x of the peak intensityof the second peak to that of the first peak satisfies 0.1≤x≤1.5. 16.The battery according to claim 14, wherein a peak position of the firstpeak is in a range of 70 eV to 73.5 eV, and a peak position of thesecond peak is in a range of 73.5 eV to 78 eV.
 17. The battery accordingto claim 14, wherein the compound containing aluminum (Al³⁺) representedby the second peak is selected from the group consisting of Al₂O₃, AlN,AlF₃, or a combination thereof.
 18. A method for preparing a positiveelectrode current collector, comprising: forming an organic supportlayer; and forming a conductive layer on a surface of the organicsupport layer, wherein the conductive layer comprises Al and at leastone modifying element selected from the group consisting of oxygen (O),nitrogen (N), fluorine (F), boron (B), sulfur (S), and phosphorus (P),or a combination thereof, wherein an X-ray photoelectron spectroscopy(XPS) spectrogram of the conductive layer has at least a first peakrepresenting elemental aluminum (Al⁰) and a second peak representing acompound containing aluminum (Al³⁺), wherein a ratio x of peak intensityof the second peak to that of the first peak satisfies 0<x≤3.0.
 19. Themethod of claim 18, wherein forming the conductive layer furthercomprises: mixing evaporated Al with a gas comprising the modifyingelement to form a compound containing aluminum (Al³⁺); and depositing Aland the compound containing aluminum (Al³⁺) onto the surface of theorganic support layer.
 20. The method of claim 18, wherein forming theconductive layer further comprises: placing an Al-based foil and theorganic support layer in a mechanical roller; introducing a gascomprising the modifying element to react with the Al-based foil to formthe compound containing aluminum (Al³⁺); and applying a pressure to bondthe Al-based foil and the organic support layer.